The present invention concerns methods and systems for medical imaging of an examination subject.
The technical problem to be solved with this invention is the imaging of parts of the patient anatomy that are moving periodically during the acquisition, for instance, due to patient breathing. In computer tomography (CT) applications, four-dimensional (4D) methods are gaining interest. Using external sensors (e.g., spirometers, etc.) the image information that is continuously being acquired is associated with position information and organized accordingly. Several three-dimensional (3D) volumes can be reconstructed corresponding to several points within the periodical motion of the patient anatomy. Not only in imaging but also in radiation therapy such methods are being used in order to optimize and reduce the radiation that is applied to the patients. Also for angiography applications, such methods would be very advantageous, as this would enable a 3D visualization of blood flow in 3D.
3D reconstruction of objects in motion using X-ray C-arm systems up to now have been limited to a few applications. For using such a system on a region of a patient that is in motion due to respiration, one possibility is to use a C-arm imaging device that can image the whole patient anatomy in a breath hold (10-20 sec), but this depends on the patient condition. This can he achieved with stationary C-arms moving with a speed up to 40 degrees/sec. Using mobile X-ray C-arms in the operating room on anesthetized patients allows breathing motion to be reduced to an absolute minimum for, e.g., the one minute of time that it takes for image acquisition.